Issue 12, 2024

One-pot reductive liquefaction of sawdust to renewables over MoOx–Al2O3 variants: insight into structure–activity relationships

Abstract

Valorization of forest residual products can offer a vital pathway to derive bio-based chemicals and fuel components. Herein, we report the effective and direct conversion of sawdust biomass over a supported Mo-oxide catalyst that results in a dominant fraction of aliphatic/cyclic alkanes and alkylbenzenes with low residual solids. The reductive liquefaction was conducted in an autoclave reactor using a series of MoOx–Al2O3 variants in the range of 340–400 °C with an initial H2 pressure of 35 bar for 4 h. At 340 °C, a correlation between Mo-loadings and reactivity for depolymerization and hydrodeoxygenation was found optimal for a surface density of 3.2 Mo-atoms per nm2 corresponding to 8 wt% Mo-loading. The liquefied fraction showed high selectivity (∼38%) for the formation of cycloalkanes and alkylbenzenes. At higher temperatures (400 °C) enhanced reactivity over the optimal catalyst showed higher cycloalkane and alkylbenzenes formation (∼57%) at a low biomass-to-catalyst feed mass ratio (3 : 1). At a higher ratio (10 : 1), alkylphenols (∼41%) are the leading product fraction followed by cycloalkanes and alkylbenzenes (∼34%) with a high liquefied monomer bio-oil product yield of 39.4 wt%. Catalyst characterization via XRD, Raman, H2-TPR, and XPS analysis revealed that the origin for this reactivity arises from the Mo species formed and stabilized over the support surface. A well dispersed, octahedral, higher fraction of easily reducible Mo-species (Mo5+) was evident over the optimal catalyst which enables enhanced C–O cleavage facilitating the hydrodeoxygenation reaction. Moreover, the solid residue yield could be reduced to below 5 wt% by optimizing the reaction conditions and particle size of the sawdust.

Graphical abstract: One-pot reductive liquefaction of sawdust to renewables over MoOx–Al2O3 variants: insight into structure–activity relationships

Supplementary files

Article information

Article type
Paper
Submitted
28 11 2023
Accepted
13 5 2024
First published
14 5 2024
This article is Open Access
Creative Commons BY license

Sustainable Energy Fuels, 2024,8, 2668-2681

One-pot reductive liquefaction of sawdust to renewables over MoOx–Al2O3 variants: insight into structure–activity relationships

M. A. Salam, Q. K. Tran, P. H. Ho, Y. W. Cheah, J. Wojtasz-Mucha, C. Kugge, E. Nejadmoghaddam, L. Olsson and D. Creaser, Sustainable Energy Fuels, 2024, 8, 2668 DOI: 10.1039/D3SE01539D

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